Motorized bicycles with small-size and high-speed are common means of transportation in a city. With two wheels arranged in a line, a conventional motorized bicycle tends to sideslip when making a sharp turn, may experience undesired drift during braking, and may easily lose balance and yaw when the bicycle is first started to move or moves slowly, thereby imposing potential danger to the rider. Therefore, a motorized tricycle or quadricycle is developed due to superior steadiness and safety thereof.